Fabricating method of transistors without dishing occurred during CMP process

Abstract

A fabricating method of transistors includes providing a substrate with numerous transistors thereon. Each of the transistors includes a gate structure. A gap is disposed between gate structures adjacent to each other. Later, a protective layer and a first dielectric layer are formed in sequence to cover the substrate and the transistors and to fill in the gap. Next, numerous buffering particles are formed to contact the first dielectric layer. The buffering particles do not contact each other. Subsequently, a second dielectric layer is formed to cover the buffering particles. After that, a first planarization process is performed to remove part of the first dielectric layer, part of the second dielectric layer and buffering particles by taking the protective layer as a stop layer, wherein a removing rate of the second dielectric layer is greater than a removing rate of the buffering particles during the first planarization process.

What is claimed is: 
     
       1. A fabricating method of transistors, comprising:
 providing a substrate with a plurality of transistors thereon, wherein each of the plurality of transistors comprises a gate structure, and a gap is disposed between gate structures which are adjacent to each other; 
 forming a protective layer and a first dielectric layer in sequence to cover the substrate and the plurality of transistors and to fill in the gap; 
 forming a plurality of buffering particles contacting the first dielectric layer, wherein the plurality of buffering particles do not contact each other; 
 forming a second dielectric layer to cover the plurality of buffering particles; 
 performing a first planarization process to remove part of the first dielectric layer, part of the second dielectric layer and the plurality of buffering particles by taking the protective layer as a stop layer, wherein a removing rate of the second dielectric layer is greater than a removing rate of the plurality of buffering particles during the first planarization process. 
 
     
     
       2. The fabricating method of transistors of  claim 1 , further comprising:
 before forming the plurality of buffering particles, performing a roughening process to roughen the surface of the first dielectric layer. 
 
     
     
       3. The fabricating method of transistors of  claim 2 , wherein the roughening process comprises a wet etching or a dry etching. 
     
     
       4. The fabricating method of transistors of  claim 1 , wherein the plurality of buffering particles comprises amorphous silicon particles, polysilicon particles, silicon germanium particle or germanium particles. 
     
     
       5. The fabricating method of transistors of  claim 1 , wherein the plurality of buffering particles are formed by a furnace annealing process or an epitaxial growth process. 
     
     
       6. The fabricating method of transistors of  claim 1 , wherein the plurality of buffering particles are formed by a furnace annealing process performed at a temperature not greater than 700° C. and an operation time of the furnace annealing process is not greater than 30 minutes. 
     
     
       7. The fabricating method of transistors of  claim 1 , wherein the substrate is divided into a dense region and an isolation region, and the gap within the dense region is smaller than the gap within the isolation region. 
     
     
       8. The fabricating method of transistors of  claim 7 , further comprising:
 forming a mask layer covering the dense region before forming the plurality of buffering particles; 
 forming the plurality of buffering particles within the isolation region; and 
 removing the mask layer before forming the second dielectric layer. 
 
     
     
       9. The fabricating method of transistors of  claim 1 , wherein each of the plurality of the transistors further comprises two source/drain doping regions embedded in the substrate at two side of the gate structure, and the gate structure comprises a dummy gate, a gate dielectric layer and a spacer, wherein the spacer surrounds the dummy gate, and the gate dielectric layer is between the dummy gate and the substrate. 
     
     
       10. The fabricating method of transistors of  claim 9 , further comprising:
 after the first planarization process, performing a second planarization process to remove the protective layer directly on the dummy gate and expose the dummy gate; 
 removing the dummy gate to form a recess; 
 forming a metal layer to fill in the recess and cover the first dielectric layer; and 
 planarizing the metal layer by taking the first dielectric layer as a stop layer to form a metal gate. 
 
     
     
       11. The fabricating method of transistors of  claim 9 , wherein the positions of the plurality of buffering particles are higher than the top surface of the dummy gate. 
     
     
       12. The fabricating method of transistors of  claim 1 , wherein a removing rate of the first dielectric layer is greater than the removing rate of the plurality of buffering particles during the first planarization process. 
     
     
       13. The fabricating method of transistors of  claim 1 , wherein the first dielectric layer and the second dielectric layer are made of the same material. 
     
     
       14. The fabricating method of transistors of  claim 1 , wherein the first dielectric layer is silicon oxide, and the second dielectric layer is silicon oxide. 
     
     
       15. The fabricating method of transistors of  claim 1 , wherein the protective layer is silicon nitride, silicon oxynitride, silicon carbide nitride or silicon carboxynitride.